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है”ह”ह

IS 11766 (1986): Method for determination of titratableacidity in milk powder and similar products (routinemethod) [FAD 19: Dairy Products and Equipment]

UDC 637.143543.257.1

IS:11766 -1986 IS0 6092 -1980

( First Reprint DECEMBER 1995) ( Reaffirmed 1992 )

hdian Standard

METHOD FOR DETERMINATION OF TITRATABLE ACIDITY IN MILK POWDER AND SIMILAR PRODUCTS ( ROUTINE METHOD ) [ IS0 Title : Dried Milk - Determination of Titratable

Acidity ( Routine Method ) ]

National Foreword

This Indian Standard which is identical with IS0 6092-1980 ‘Dried milk - Determination a titratable acidity ( Routine method )‘. issued by the International Organization for Standardization ( IS0 ), was adopted by the Indian Standards Institution on the recommendations of the Dair Products Sectional Committee and approval of the Agricultural and Food Products Division Council.

In the adopted standard certain terminology and conventions are not identical with those usec in Indian Standard; attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear, referring to this standard, it should bc read as ‘Indian Standard’; and

b) Comma ( , ) has been used as decimal marker while in lndian Standards, the current practict is to use full point ( . ) as the decimal marker.

Zross References

International Standard IS0 707-1985 Milk and milk products -

Sampling

Corresponding Indian Standard IS : 11546-l 985 Methods of sampling of milk

and milk products ( Identical )

ISO’R 1736 Dried milk - Determination of fat content ( Reference method )

IS : 11721-1986 Method for determination oi fat content in milk powder and similar products ( Reference method ) ( Identical )

ISOjR 6091 Dried milk - Determination of titratable acidity ( Reference method)

IS : 11765-1986 Method for determination of titratable acidity in milk powder and similar products ( tdentical )

ln reporting the result of a test or analysis made in accordance with the standard, if the final alue, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960 3ules for rounding off numerical values ( revised)‘.

Adopted 19 Mdv 1986 I

Q April 1987, BIS I

Or 2

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ~AFAR MARG

NEW DELHI 110002

IS: 11766 - 1986 IS0 6092 - 1980

1 Scope and field of application

This International Standard, specifies a routine method for the

determination of the titratable acidity of all types of dried milk.

2 References

ISOlR 707, Milk and milk products - Sampling.

ISOIR 1736. Dried milk - Determination of fat content

(Reference method).

IS0 6091, Dried milk - Determination of titratable acidity

(Reference method).

3 Definition

tit&able acidity of dried milk : The number of millilitres of 0,l mol/l sodium hydroxide solution required to neutralize, in the presence of phenolphthalein, aa quantity of the reconstitu-

ted milk corresponding to 10 g of solids-not-fat, until the

appearance of a pink coloration.

4 Principle

Preparation of reconstituted milk by addition of water to a test

podon of dried milk corresponding accurately to 5 g of solids-

not-fat. Titration with 0.1 mol/l, sodium hydroxide solution

using phenolphthalein as indicator and cobaltIll) sulphate acr

reference colour solution. Mtiltiplication of the number of milli-

litres used in the titration by the factor 2, in order to obtain the

number of millilitres in terms of 10 g of solids-not-fat.

The amount of sodium hydroxide solution required is a function

of the amount of natural buffering substances present in the

product, and of developed or added acid or alkaline substan-

CeS.

5 Reagents

All reagents shall be of recognized analytical quality. Water

shall be distilled or deionized water, freed from carbon dioxide

by boiling for 10 min before use.

5.1 Sodium hydroxide, standard volumetric solution,

c(NaOH) = 0.1 f 0,000 2 mol/l.lj

5.2 Reference colour solution.

Dissolve 3 g of ‘cobalt(ll) sulphate heptahydrate (CoS04.7H20)

in water and make up to 100 ml.

5.3 Phenolphthalein solution.

Dissolve 2 g of phenolphthalein in 75 ml of 95 % ( V/ VI ethanol

and add 20 ml of water. Add the sodium hydroxide solution

(5.1) until 1 drop gives a faint pink coloration, and make up to

100 ml of water.

6 Apparatus

6.1 Analytical balance.

6.2 Burette, graduated in 0,l ml and with an accuracy of

0.05 ml.

6.3 Pipettes, of capacity 2 ml

6.4 Measuring cylinders, of capacity 50 ml

6.5 Conical flasks, of capacity 100 or 150 ml, with ground

necks and ground glass stoppers.

1) Hitherto expressed as “0,l + 0,000 2 N standard V~ILI~BI~IC solution

2

IS: 11766 - 1986 IS0 6092 - 1980

7 Sampling

See GO/R 707.

8 Procedure

8.1 Preparation of the test sample

Transfer the sample to a clean, dry container (provided with an

air-tight lid) of capacity about twice the volume of the sample.

Close the container immediately, and thoroughly mix the con-

tents by repeatedly shaking and inverting the container. During

these operations, exposure of the sample to the atmosphere

should be avoided as far as possible, to minimize adsorption of

water.

8.2 Test portion

Weigh BlO/a) f 0,Ol g of the test sample (8.1) into each of two conical flasks (6.51, u being the solids-not-fat content of

the sample, expressed as a percentage to two decimal places.

NOTE -- The solids-not-fat content of the sample may be calculated by subtracting the fat content (determined in accordance with

ISO/R 17361 and the moisture content’) from 100.

8.3 Determination

8.3.1 Prepare reconstituted milk by adding 50 ml of water at

about 20 OC to the test portion (8.2) and agitatinq vigorously.

Allow to stand for about 20 min.

8.3.2 Add $-one of the conical flasks 2 ml of the reference

colour solution (5.2) to obtain a colour standard, and mix by

slight swirling.

If a series of determinations on similar products is to be carried

out, this colour standard may be used throughout. However it

should be discarded after 2 h.

8.3.3 Add 2 ml of the phenolphthalein solution (5.3) to the

second conical flask, and mix by slight swirling.

8.3.4 Titrate the contents of the second conical flask, while

swirling, by adding the sodium hydroxide solution (5.1) from

the burette (6.2) until a faint pink colour similar to that of the

colour standard persists for about 5 s. Th’e titration should be

completed within 45 s

Record the volume, in millilitres, of sodium hydroxide solution

used, to the nearest 0,05 ml.

9 Expression of results

9.1 Method of calculation

The titratable acidity is equal to

2x v

and formula

where V is the volume, in millilitres, of the sodium hydroxide

solution (5.11 used for titration (8.3.41.

Express the result to one decimal place.

9.2 Repeatability

The difference between the results of two determinations car-

ried out simultaneously or in rapid succession by the same

analyst shall not exceed 0,4 ml of 0.1 mol/I sodium hvdroxide

solution per 10 g of solids-not-fat.

10 Comparison with the reference method

Verify at intervals whether this routine metnod gives results in

adequate agreement with those obtained using the reference

method specified in IS0 6091.

11 Test report

The test report shall show the method used and the result ob-

tained. It shall also mention any operating conditions not

specified in this International Standard, or regarded as op-

tional, as well as any circumstances that may have influenced

the result.

The test report shall include all details required for the complete

identification of the sample.

1) A method for the determination of moisture content 1s spectfwd in IDF Standard No 26. Deternvnar~on of the wa?er cnr~renf of &red mdk, whtch

IS currently under rev~ston by a jotnt IS0 IDF/AOAC group of experts.

3 Reprography Unit, BIS, New Delhi, India

AMENDMENT NO. 1 OCTOBER 1997 TO

IS 11766 : 1986/iSO 6092 - 1980 METHOD FOR DETERMINATION OF TITRATABLE ACIDITY IN

MILK POWDER AND SIMILAR PRODUCTS (ROUTINE METHOD)

(Page 1, NatiodForfword) - Insert the following at the end:

‘For calculating the titratable acidity in terms of percentage, the following formula may be used:

Percentage &ratable acidity ( as Lactic Acid ) = 0.09 x 2 x V

where

V = volume in millilitres of sodium hydroxide solution used for titration.’

(FAD57)

Reprography Unit, BIS. New Delhi, India